This invention relates to an apparatus for manufacturing magnetic recoding disks. Especially, this invention relates to an apparatus performing a manufacturing method including a step of removing protrusions on a substrate and a step of forming a lubricant film on the substrate.
The manufacture of a magnetic recording disk such as a hard disk is roughly divided into former steps and latter steps. The former steps include deposition of an underlying film, deposition of a magnetic film for a recording layer, and deposition of an overcoat. The latter steps include preparation of a lubricant layer and other required steps. The lubricant layer is prepared considering contact of a magnetic head onto the disk in read-out.
The preparation of the lubricant layer is carried out by a following procedure.
To begin with, a substrate is taken out to the atmosphere after deposition steps because thin-films such as the magnetic film for a recording layer are usually deposited in a vacuum chamber. Then, burnishing is carried out to remove contaminants adhering to the substrate and to remove protrusions formed on the substrate during the film depositions. The burnishing is a step of removing the protrusions and the contaminants from the substrate by rubbing it with a tape-shaped polishing member. The “contaminant” in this specification means materials that may contaminate a substrate in general, which is a gas, ions, molecules, particles or other substances.
The lubricant layer is prepared after the burnishing. As lubricant, fluorine lubricant such as perfluoropolyether (PFPE) is used. Such lubricant is diluted with solvent for improving uniformity. The diluted lubricant is coated onto the substrate by such method as a dipping method where the substrate is dipped into the diluted lubricant, or a spin-coating method where the lubricant is dropped onto the substrate when it is spun.
“Substrate” means a board that consists a magnetic recording disk in this specification. “Surface of substrate” may mean a surface of a film or layer when a film deposition or a layer preparation has already been carried out onto the substrate.
Recent improvement of recording density in magnetic recording disks is remarkable. For example, in hard disks it is becoming 20 gigabit/inch2 in the year 2000 and 40 gigabit/inch2 in the year 2001. One of factors that enable the improvement of the recording density is to reduce a spacing. FIG. 19 shows a view explaining the spacing.
In FIG. 19, the spacing in the case of hard disks is explained as an example. As shown in FIG. 19, a hard disk has a structure where a recording layer 91 is prepared on a substrates 9, an overcoat 92 is deposited on the recording layer 91, and a lubricant layer 93 is prepared on the overcoat 92. A magnetic head for writing and reading information is located at a position slightly apart from the surface of the hard disk. The spacing, which is designated by “S” in FIG. 19, means distance between a write-readout device element 900 of the magnetic head and the recording layer 91 of the hard disk. A distance between the write-readout device element 900 and the lubricant layer 93 is called a “flying height”, which is designated by “FH” in FIG. 19. It is important to make the spacing S small in improving the recording density.
As the spacing S becomes smaller, demands to the manufacturing process have been becoming severer by years. For reducing the spacing S, it is required not only to reduce the flying height FH, which is about 10 to 20 nm in a typical hard disk drive (HDD) currently on sale in the market, but also required to make a thickness of the overcoat 92 and a thickness of the lubricant layer 93 thinner. As thickness of the overcoat 92 is made thinner, it is required to deposit a more compact and harder film as the overcoat 92. As the thickness of overcoat 92 is made thinner, a demand for thickness uniformity of the lubricant layer 93 becomes severer as well as a demand for enhancing an adhesion strength of the lubricant layer 93 becomes severer.
With the above described points in the background, a method for depositing the overcoat 9 has been shifting from a conventional sputtering method to a chemical vapor deposition (CVD) method. Usually a carbon film is deposited as the overcoat 92. By the CVD method, it is enabled to deposit a carbon film called a “diamond-like carbon” (DLC) film. The DLC film is known as a hard, compact and stable carbon film even when its thickness is small. This is the reason why the method has been shifting to the CVD method.
However, the contaminants of gases or ions may adhere to the overcoat 92 under influence of residual gases when it is deposited by the CVD method. In addition, minute protrusions are easily formed on the overcoat 92 in the CVD method, resulting from abnormal film growth. If the lubricant layer 93 is prepared over the overcoat 92 on which the contaminants or the protrusions exist, there easily arise problems such as the adhesion strength of the lubricant layer 93 may decrease, and the thickness of the lubricant layer 93 may lose uniformity.
The adhesion strength of the lubricant layer 93 is enhanced when terminal groups of macromolecules composing the lubricant are bonded sufficiently with carbons in the overcoat 92. For making the adhesion strength higher, it is preferable that the macromolecules are bonded with carbons in the surface of the overcoat 92 at one of or both terminal groups. On the other hand, it is desirable that a degree of freedom of the macromolecules is high at a portion adjacent to the surface of the lubricant layer 93, on purpose of prevention the write-readout device element 900 of the magnetic head from chucking with the disk. In short, both terminal groups are preferably not bonded near the surface of the lubricant layer.
A macromolecule bonded with a carbon at one of or both terminal groups is hereinafter called a “bonded lub”. A macromolecule not bonded with a carbon at either of terminal groups is hereinafter called a “free lub”. A thickness ratio of the bonded lub layer against the whole lubricant layer 93 is hereinafter called a “bonded ratio”. Though an optimum bonded ratio has been supposed about 20-30% so far, a demand for accuracy of the bonded ratio tends to be severer as the lubricant layer 93 is made thinner.
For obtaining the demanded bonded ratio, it has been attempted to carry out treatment for controlling the bonds of the terminal groups after the lubricant-layer preparation. In this treatment, thermal energy or light energy is applied to the lubricant layer 93, thereby controlling the bonds of the terminal groups. This treatment is hereinafter called “post-preparation treatment”.
However, when the overcoat 92 is exposed to the atmosphere after the deposition, many contaminants of gases or ions in the atmosphere are adsorbed with the surface of the overcoat 92 because the surface has been chemically activated. As a result, when the lubricant layer 93 is prepared, a contaminated layer may be formed between the lubricant layer 93 and the overcoat 92. If the contaminated layer is formed, it may become difficult to obtain an accurate bonded ratio by the post-preparation treatment. For preventing these problems, equipment that reduces the contaminants is required. Including such a point, the current situation is that huge investment is inevitable for coordinating manufacture environment.
An object of the invention is to solve the described problems in the manufacturing process, which have been brought from the reduction of the spacing.